How Laser Cleaning Works
The method of laser cleaning relies on taking advantage of the fact that various materials will absorb different wavelengths of light depending on properties such as their color and chemical composition. Laser parameters can be tuned to selectively remove a layer of unwanted material from the original surface that does not get affected by the same laser parameters.
Examples of unwanted layers of material include corrosion, soiling, graffiti, and coatings on monuments. Unlike mechanical or abrasive cleaning methods which rely on mechanically impacting the surface to get contaminants to break free, this method relies on using light to excite the contaminant so that it separates from the surface on its own.
Tuning a laser cleaning system can result in a variety of effects that can aid in the removal of an unwanted layer such as contaminants, corrosion, coatings, or paint. The goal is for the laser to discriminate between the unwanted layer and the substrate. Ideally the unwanted layer absorbs the laser pulses while the original substrate reflects them. Once the laser reaches the substrate, it does not absorb into it and simply reflects off the surface. Laser cleaning is a surface cleaning technique and it will not, for example, remove stains that have penetrated into a surface.
Laser cleaning relies on calibrating laser parameters to selectively remove unwanted layers of material or coatings. The following steps are shown above:
The contaminant layer (red) needs to be removed from the original substrate (green).
Laser parameters are calibrated to ablate away the contaminant without damaging the substrate.
The substrate is uncovered to reveal a clean and undamaged surface.